The present invention relates to deicing systems for aircraft.
In northern climates during winter months, aircraft which either are parked on the ground overnight or which are on the ground during severe winter weather, frequently accumulate snow or ice on the airfoil surfaces. It is, naturally, necessary to remove this material prior to takeoff and such removal has been the subject of a variety of deicing equipment in the prior art.
The most popular equipment has been the utilization of a self-contained vehicle, such as a truck, having an extensible boom mounted thereon and including a tank containing a mixture of water with a deicing fluid such as ethylene glycol or propylene glycol or mixtures thereof and which is heated to from 160.degree. to 190.degree. F. by a self-contained tank heater on the truck. The heating deicing fluid is then pumped through a hose and nozzle to the end of the extensible boom where the operator directs a stream of the heated deicing fluid mixture onto the aircraft. This removes the snow and/or ice and provides a coating of glycol largely preventing further formation of the freezing substance. This deicing procedure normally takes place just prior to the plane's departure after which the aircraft's normal internal electrical deicing systems are employed. With such vehicles, the tank size is, of necessity, limited and once emptied, the recovery time for reheating deicing fluid added to the tank is significant and causes highly undesirable delays in aircraft departure. Representative of such a deicing system is German Patentschrift No. 767,362, published June 13, 1952. The capital investment for several vehicles necessary to properly maintain an air service with such a system can be prohibitive. Also, the tank heaters have been gasoline powered and have presented a significant safety hazard.
Other non-portable deicing systems have been proposed and are represented by U.S. Pat. Nos. 3,533,395, issued Oct. 13, 1970, to Edward E. Yaste, and 3,612,075, issued Oct. 12, 1971, to Vernon H. Cook. Both of these patents disclose fixed installation systems whereupon an aircraft is brought into a deicing station with boom structures having a plurality of nozzles for spraying heated deicing fluid over the aircraft surfaces and recovering the fluid and recirculating it after filtration, concentration, and reheating. These systems have the advantage of providing larger volumes of deicing fluid and hence little or no recovery delays but the disadvantage that the installation is extremely expensive and requires each aircraft to move through the deicing station remote from the ramps prior to takeoff. This, naturally, can involve a significant delay and therefore such prior art has not represented a commercially successful solution to the deicing problem.